Protected 3,5-dihydroxy-2,2-dimethyl-valeroamides for the synthesis of epothilones and derivatives and process for the production and the use

ABSTRACT

The invention relates to new protected 3,5-dihydroxy-2,2-dimethyl-valeroamides for the synthesis of epothilones and derivatives and process for the production and the use of the new compounds for the production of epothilones or epothilone derivatives.

This application claims the benefit of the filing date of U.S.Provisional Application Ser. No. 60/313,015 filed Aug. 20, 2001.

The invention relates to the subject that is characterized in theclaims, i.e., new intermediate products and process for their productionand the use. The process for the production of new intermediate productsstarts from economical starting materials, yields the intermediateproducts in high enantiomer purities, in high chemical purity, in goodyields, and allows the industrial-scale production.

The invention is used in the synthesis of component A from natural andsynthetically modified epothilones or derivatives. Epothilones are16-membered macrolide rings that were isolated from the cultures ofMyxobacterium Sorangium Cellosum and are representatives of a class ofpromising anti-tumor agents that were tested and found to be effectiveagainst a number of cancer lines. A survey of the syntheses has beendescribed by J. Mulzer et al. in J. Org. Chem. 2000, 65, 7456-7467.

In the literature, in addition to the natural epothilones, a number ofsynthetic epothilone derivatives are described that vary for the mostpart within radicals M and T. In most cases, M stands for a heterocyclicradical here. Most syntheses of the natural epothilones and thesynthetic epothilone derivatives use the A-component fragment, whichrepresent carbon atoms C₅-C₁₀ in the macrolide. Within this component A(see below), C₁ is the C₅ in the macrolide and C₆ is the C₁₀ in themacrolide, etc.

Within the component, T stands for a C₁-C₄ alkyl or alkenyl radical, andSg1 and Sg2 stand for the protective groups that are familiar to oneskilled in the art, such as, e.g., the TBDMS group.

A possible production of the A-component is described in, for example,WO00/58254 (University of Wisconsin). A synthesis of β-keto esters,which can be converted into multistage sequences in component A, isdisclosed therein. The chirality is introduced by an asymmetrichydrogenation of a β-keto ester according to Noyori:

In this connection, the conversion of the ester group into a ketone canonly be done by means of a multistage sequence. In this case, after aprotection of the 1- and 3-hydroxy group, the ester group (C-5 atom) isreduced to form alcohol, the oxidation to aldehyde is carried out, theGrignard addition of an alkyl radical with an alkylmagnesium oralkyllithium compound yields a secondary alcohol, which then isoxidized. To get from the ester to the ketone, a total of 6 steps arenecessary. The direct reaction of an ester is not selective, since theintermediately produced product is further reacted. The followingdiagram shows the entire synthesis pathway:

Another method for creating component A is described by B. Paniker etal. in Tetrahedron 2000, 56, 7859-7868. It is described there that thealdol reaction with a chiral component yields a less selective reaction.By the round-about way of an N-methylthioacetyl-oxazolidinone, thesynthesis of the chiral C3 atom in a multistage sequence with improveddiastereoselectivity by means of boron enolate is described. To achieveusable diastereoselectivities, a methylthio substitution is necessary;the thio ether is cleaved off after the aldol reaction.

Further, a sequence can be found in the prior art (R. E. Taylor, Y.Chen, Org. Lett. (2001), 3(14), 2221-2224) in which a phenyl ester isused. The yield that is achieved in this case is indicated with 77%. Inthe example that is described by A. Fürstner in Chem. Comm. 2001,1057-1059, a 67% yield is achieved. These yields of the methods from theprior art are significantly less than those of this invention.

In J. Org. Chem. 2000, 65, 7456-7467, an asymmetrical synthesis of aβ-keto ester is further described, whereby a variant in asymmetricalform is performed as an aldol reaction. In this method, D-Ts-valine isused as a catalyst, which can be produced from the expensive amino acidD-valine. This method yields an ee-value of 90%. An asymmetrical aldolreaction, in which the yield is 71%, is described by R. E. Taylor, Y.Chen, Org. Lett. (2001), 3(14), 2221-2224 as another example in thisregard.

Another method for the production of a double TBDMS-protectedA-component-ethyl ketone is finally described by Nicolaou in Chem. Eur.J. 2000, 6, 2783-2800.

This invention includes the object of being able to produce auniversally usable starting intermediate compound of general formula Ias well as the optically pure antipodes of general formulas Ia, Ib,

in which R1, R2 can be the same or different and, independently of oneanother, stand for an alcohol protective group that is familiar to oneskilled in the art, for example, benzyl, 4-methoxybenzyl,3,4-dimethoxybenzyl, THP, TBDMS, TMS, TES, TIP, TBDPS, MEM, MOM, allyl,trityl, or, in the case when R1 and R2 are bridged, stand for a ketalprotective group, such as, e.g.,

Y stands for a group -NA1A2, whereby A1 and A2, independently of oneanother, stand for the radicals C1-C6 alkyl, such as methyl, ethyl,propyl, or aryl or aralkyl, such as phenyl, benzyl, OH, OMe, O-benzyl orfor a radical

to produce A-component fragments for epothilone total syntheses.

To this end, compounds of general formula I are reacted as describedbelow:

The reactions of the compounds of general formula I, as well as theirantipodes Ia, Ib to form ketones AK are carried out with methyllithiumor methyl-Grignard compounds according to the standard process that isknown to one skilled in the art; the aqueous working-up then yields theketone. The subsequent alkylation with an alkyl or alkenyl-halide offormula T-Hal (Hal=Cl, Br, I or tosylate, mesylate, triflate, etc.) withthe addition of a base yields the A-component fragments.

A can also be directly obtained, however, by the amides of generalformula I being reacted directly with organometallic compounds, such as,e.g., the lithium compound Li—CH2-T and then being worked up in aqueousform.

As a rule, the above-described reactions run smoothly and produce theA-components in high yields.

There was therefore a need for an industrial-scale process that allowsit to prepare a universally usable intermediate compound for theproduction of the A-component in the epothilone total synthesis.

In addition to the high yields in the conversion into the A-components,the relatively easy accessibility of the compounds of general formula Ifrom relatively inexpensive starting materials is emphasized. Moreover,the compounds according to the invention are stable in storage incontrast to the esters and ketones that are known in the literature andare, for the most part, crystalline solids and can be purified bycrystallization. In this way, high chemical and optical yields(e.e.>98%) can be achieved.

Variant I (General Access via Aldol Reactions)

a) In the case where R1 and R2 stand for a ketal protective group, or R1=R2, compounds of general formula I can be produced from compounds ofgeneral formula II

whereby Y has the above-mentioned meaning,according to the methods for protective group chemistry that are knownto one skilled in the art; thus, for example, their production andcleavage are described by P. J. Kocienski in “Protecting Groups,” GeorgThieme Verlag Stuttgart, New York, 1994, as well as in Houben Weyl, 4thEdition, Volume VI/1b, p. 737, Thieme Stuttgart 1984.

b) In the case that R1 and R2 do not represent any ketal-protectivegroup but nevertheless can be the same or different, the production ofthe compounds of general formula I can be carried out directly from thecompounds of general formula III, by protective group R2 beingintroduced according to methods that are known in the literature (J.Mulzer et al., J. Org. Chem. 2000, 65, 7456-7467).

Compounds of general formula II can be produced from compounds ofgeneral formula III

in which Y stands for the above-indicated meaning, and R1 stands for aprotective group in the above-indicated meaning, by cleavage ofprotective group R1 according to the process, known to one skilled inthe art, of the protective group cleavage of alcohols (P. J. Kocienskiin “Protecting Groups,” Georg Thieme Verlag Stuttgart, New York1994/Houben Weyl, 4th Edition Volume VI/1b p. 737, Thieme Stuttgart1984).

Compounds of general formula III can be produced from compounds ofgeneral formula IV

by reaction of the compounds of formula V

in which Y and R1 are in the above-indicated meaning, and L stands for asilyl protective group, such as, e.g., TBDMS, TMS, TES, TIP, TBDPS,in a way that is known to one skilled in the art by the techniques ofaldol condensation. (C. H. Heathcock in Modem Synthesis Methods, 1992(Editors R. Scheffold, VHCA Basel 1992, pp. 1-102).

The production of compounds of general formula IV are known to oneskilled in the art, however:

R1: THP in JOC, 1984, 49, 2301-2309

R1: benzyl in J. Chem. Soc. Perk. Trans 1, 2000, 2429-2454,

R1: TBDMS in JOC, 2000, 65, 7456-7467

The production of compounds of general formula V is novel and isdescribed in the examples.

Variant II (Production of Optically Active Intermediate Products ofGeneral Formula Ia)

For the production of optically active compounds of general formula Ia

the procedure is analogous to that described under Variant I. Startingfrom the optically active intermediate stage of general formulas IIa andIIIa

compounds of general formula Ia are produced.

Compounds of general formula IIa are produced analogously from theoptically active precursors of general formula IIIa

Optically active compounds of general formula IIIa are accessible asfollows:

-   -   1. Separation of the racemic compound of general formula III in        the chiral phase (Lit.: G. Roussel, P. Pirs, Chirabase, Pure and        Applied Chemistry, 1993, 65, 235-244), primarily by SMB        technique: (A. Seidel-Morgenstem et al., Chromat. A. 1998,        827/2, 175-191).    -   2. Starting from the racemic alcohol of general formula III, by        esters of general formula VI    -    in which R3 stands for a C₁-C₆ alkyl group or an allyl, phenyl        or benzyl group, being produced according to the process of        esterification that is known to one skilled in the art, and the        latter being saponified enantioselectively by enzymatic or        microbiological methods. The alcohol that is produced is clearly        distinguished in its Rf value from the ester that is used so        that the two can easily be separated from another, e.g., by        column chromatography.    -   3. By aldol condensation that is mediated with chiral catalysts,        by compounds of general formulas IV and V being reacted with use        of a catalytic or stoichiometric amount of a chiral aldol        catalyst:        -   Literature: See, e.g., J. Org. Chem. 2000, 65, 7456-7467.    -   4. By a chiral reduction of the ketone of general formula VII        being performed according to methods that are known to one        skilled in the art. Lit.: Noyori et al., J. Am. Chem. Soc. 1987,        109, 5850; Noyori et al., J. Am. Chem. Soc. 1988, 110,        629, R. C. Larock in “Comprehensive Organic Transformations,”        VCH Publishers New York 1989, ISBN 0-89573-710-8, pages 540-548.

Compounds of general formula VII, with R1 and Y in the above-indicatedmeaning, can be obtained by reaction of the compounds of general formulaV with compounds of general formula VIII

in which Nu stands for a leaving group, such as Cl, Br, imidazole, —OPh,—O—C6H4NO2, —O—C1-C4 alkyl, etc.

The reaction is carried out in a way that is known to one skilled in theart. Lit.: Ann. 1962, 655, 90, R. C. Larock in “Comprehensive OrganicTransformations,” VCH Publishers New York 1989, ISBN 0-89573-710-8,pages 685-702.

The production of compounds of general formula VIII is described in theliterature: J. Med. Chem. 1999, 706-721.

In some cases, it has proven advantageous when compounds of generalformula VII are produced by oxidation from the racemic alcohols ofgeneral formula II according to the methods of oxidation that are knownto one skilled in the art (e.g., Swern oxidation, PDC, PCC, etc.).

In some cases, it has proven advantageous when compounds of generalformula V are reacted with propiolactone to form compounds of generalformula IX:

Compounds of general formula IX can be converted very easily intocompounds of general formula VII by introducing protective groupsaccording to the methods that are known to one skilled in the art (see:P. J. Kocienski described in “Protecting Groups,” Georg Thieme VerlagStuttgart, New York 1994, as well as in Houben Weyl, 4th Edition, VolumeVI/1b, p. 737, Thieme Stuttgart 1984).

Starting from compounds of general formula IX, however, compounds ofgeneral formula IIa

can also be obtained by the keto group being reduced chirally withchemical or microbiological methods (e.g., according to: J. Org. Chem.1985, 50, 127/J. Chem. Soc., Chem. Commun. 1987, 1368).Variant III

Compounds of general formula Ia

can also be produced by introducing protective groups according tomethods that are known in the literature for introducing alcoholprotective groups from the compounds of general formula X

(see literature cited above for introducing protective groups).

Compounds of general formula X can be produced from compounds of generalformula XI

in which R4 stands for a methyl, ethyl or benzyl group,by ester reduction according to methods that are known to one skilled inthe art. Lit.: R. C. Larock in “Comprehensive Organic Transformations,”VCH Publishers New York 1989, ISBN 0-89573-710-8, pages 549-551).

Compounds of general formula XI can be produced from compounds ofgeneral formula XII

in which R4 stands for a C₁-C₆ alkyl, methyl, ethyl, tert-butyl, phenylor benzyl group, by introducing protective group R2 according to methodsthat are known to one skilled in the art (see above).

Compounds of general formula XII can be obtained from β-keto esters ofgeneral formula XIII

by methods of chiral reduction (chemical or enzymatic). Lit.: Chemie inunserer Zeit [Chemistry in Our Time], 1996, 30, 201-213, R. C. Larock in“Comprehensive Organic Transformations,” VCH Publishers New York 1989,ISBN 0-89573-710-8, pages 540-547).

Compounds of general formula XIII are obtained by reaction of compoundsof general formula XIV with compounds of general formula V

Compounds of general formula XIV are known in the literature: Compoundsof general formula V are novel, for production see above and theexamples, or can also be obtained from the reaction of compounds ofgeneral formulas XIIIa and XIIIb.

Here, Nu is in the meaning of the leaving group that is alreadymentioned above, and Q stands for a hydrogen atom or a COOH group. If Qis a hydrogen atom, XIIIa is deprotonated with an organic base, such as,e.g., LDA and then is reacted with the activated acid derivativeaccording to the methods that are familiar to one skilled in the art.

In the case of Q being equal to COOH, the procedure is performed withthe methods of the malonic acid-semi-ester condensation, as describedin, e.g., J. Am. Chem. Soc. 1999, 121, 7050-7062, Synth. Commun. 1997,27, 3227-3234.

Compounds of general formula XIIIa are commercially available (e.g.,Aldrich).

Compounds of general formula XIIIb are produced as described in R. C.Larock in “Comprehensive Organic Transformations,” VCH Publishers NewYork 1989, ISBN 0-89573-710-8, pages 963-964).

In some cases, it has proven advantageous to run the diols of generalformula IIa

directly through the compounds of general formula XII

by reduction of the ester group according to the above-mentionedprocess.

The production of the racemic diol of general formula II can also use asstarting compounds β-keto esters of general formula XIII

according to the commonly used methods for reduction of esters andketones.Variant IV

For the production of optically active diols of general formula IIa, ithas proven advantageous to undertake a chromatographic separation orcrystallization of the diastereomeric ketals of general formulas XIVaand XIVb

in which A is taken for the radical of an optically active ketone, suchas, e.g., (−) menthone, (−) camphor, etc., and then the ketal group iscleaved off according to the methods of protective group chemistry thatare known to one skilled in the art.

The production of diastereomeric 1,3 diol-ketals of general formulasXIVa and XIVb is carried out from the racemic diol of general formula IIby reaction with chiral ketones according to processes that are known inthe literature. Lit.: T. Harada et al., J. Org. Chem. 1992, 57,1412-1421.

Of course, the corresponding enantiomer compounds of general formula Ib

can also be produced with use of mirror-image catalysts or other enzymesystems.

There is also the possibility of obtaining the corresponding enantiomersin intermediate stages of general formula IIIb

by inversion of the hydroxyl group (e.g.) according to Mitsunobu (Lit.:O. Mitsunobu, Synthesis 1981, 1-28).

Of protective groups R1 and R2 that are used in the synthesis, inparticular the benzyl group and the TBDMS group are preferred. In thecase that R1, R2 stands for a ketal protective group, especially—(C(CH3)2)- is preferred.

Group Y can preferably stand for the radicals:

but the dimethylamino group is especially preferred.

Of the different production variants here, the following partialsequences are especially preferred for the creation of achiralprecursors:

-   -   1. Production of the compounds of general formula VII from the        intermediate stages of general formulas V and VIII        -   L in the meaning of TMS, R1=benzyl, Nu=Cl, Y=dimethylamino    -   2. Production of the compounds of general formula XIII from        compounds of general formulas V and XIV.        -   L in the meaning of TMS, R4=ethyl, Nu=Cl, Y=dimethylamino    -   3. Production of the compounds of general formula VII by aldol        condensation and subsequent oxidation        -   L in the meaning of TMS, R1=benzyl, Nu=Cl, Y=dimethylamino    -   4. Production of the compounds of general formula IX (with        Y=dimethylamino)

For the production of chiral precursors, especially the partial stepsthat are indicated below are preferred:

-   -   1. Chiral aldol condensation with a chiral catalyst    -   2. Enantioselective saponification of an acetate with the aid of        an enzyme    -   3. Chiral reduction of a β-keto amide (Noyori type)    -   4. Chiral reduction of the β-keto ester with subsequent        reduction

The production of the compounds according to the invention is carriedout preferably in the sequences that are described below:

-   -   1. Production of acetone ketals    -   2. Production of the Di-TBDMS-protected compound

The production of the compounds and process according to the inventionis to be explained in more detail in the embodiments below.

Without further elaboration, it is believed that one skilled in the artcan, using the preceding description, utilize the present invention toits fullest extent. The following preferred specific embodiments are,therefore, to be construed as merely illustrative, and not limitative ofthe remainder of the disclosure in any way whatsoever.

In the foregoing and in the following examples, all temperatures are setforth uncorrected in degrees Celsius and, all parts and percentages areby weight, unless otherwise indicated.

EXAMPLE 1A 1-Dimethylamino-2-methyl-1-trimethylsilyl-propene

294 ml (0.45 ml) of butyllithium is added in drops at −35° C. underinert gas to 0.43 mol of diisopropylamine in 300 ml of THF. Then, 50 g(0.434 mol) of N,N-dimethyl-2-methylpropinoic acid amide is added indrops at 0° C. and stirred for 30 minutes at this temperature. Then,60.3 ml (0.47 mol) of trimethylsilyl chloride is added at −35° C. andstirred for two more hours. The solvent is distilled off in a rotaryevaporator. The residue is distilled in a vacuum at 65-69° C./30 mbar.

¹H-NMR (300 MHz, CDCl₃, 25° C., TMS), δ=0.2 (s, 9H), 1.53 (s, 3H), 1.63(s, 3H), 2.5 (s, 6H)

Elementary analysis: C H Cld. 57.70 11.30 Fnd. 58.00 11.40

EXAMPLE 1b rac.N,N-Dimethyl-(5-benzyloxy-2,2-dimethyl-3(R,S)-hydroxy-pentanoicacid)amide

68.8 g (0.367 mol) of 1-dimethylamino-2-methyl-1-trimethylsilyl-propeneof the title compound of Example 1a, 67 g of benzyloxy-propanol (0.4mol) and 5.56 g>>ZnCl₂ are stirred in 500 ml of THF for 1 hour. 13.88 gof NH₄F and 300 ml of MeOH are added and stirred for 18 hours at roomtemperature. It is distilled off, the residue is extracted with 200 mlof ethyl acetate, and the organic phase is washed with 10% citric acidsolution. After chromatography on silica gel with ethyl acetate/hexaneas an eluant, 60.8 g of product is obtained (60% of theory).

Elementary analysis: C H Cld. 68.79 9.02 Fnd. 68.80 9.00

EXAMPLE 1c N,N-Dimethyl-(5-benzyloxy-2,2,-dimethyl-3-oxy-pentanoicacid)amide

2.47 g of oxalyl chloride is cooled in 25 ml of methylene chloride to−60° C., 4.4 ml of DMSO in 10 ml of methylene chloride is added, and itis stirred for 15 more minutes; 7.26 g ofN,N-dimethyl-(5-benzyloxy-2,2-dimethyl-3-hydroxy-pentanoic acid amide)of the title compound of Example 1b is added in 20 ml of methylenechloride, and it is stirred for 30 more minutes. 8.7 ml of triethylamineis added in drops, and it is stirred for 30 more minutes while beingheated to −20° C. It is hydrolyzed with 25 ml of water, and the phase isseparated. After the solvent is evaporated, 7.18 g of product isobtained. After chromatography, 3.6 g of product (50% of theory) isobtained, in addition to 1.36 g of educt.

Elementary analysis: C H Cld. 69.29 8.36 Fnd. 69.40 8.50

EXAMPLE 1d N,N-Dimethyl-(5-benzyloxy-2,2,-dimethyl-3(S)-hydroxy-pentanoic acid)amide

500 mg of N,N-dimethyl-(5-benzyloxy-2,2,-dimethyl-3-oxy-pentanoicacid)amide of the title compound of Example 1c is hydrogenated with acatalyst (produced from 23.3 mg of RuCl₂ (Ph)₂ and 62.6 mg of S.-BiNAPaccording to R. Selke, Angew. Chem. [Applied Chemistry] 1998, 110,1927-1930) (2 days at 40° C./100 bar).

Yield: quantitative

Elementary analysis: C H Cld. 68.79 9.02 Fnd. 69.00 9.00

EXAMPLE 1e N,N-Dimethyl-3(S)-(3,5-dihydroxy-2,2,-dimethyl-pentanoicacid)amide

13.13 g (47.70 mmol) ofN,N-dimethyl-(5-benzyloxy-2,2,-dimethyl-3(S)-hydroxy-pentanoicacid)amide of the title compound of Example 1d, dissolved in 110 ml oftetrahydrofuran, is added to 16 g of Pearlman's catalyst (Pd(OH)₂ oncarbon, 20%). It is now hydrogenated for 7.5 hours at 10 bar and at roomtemperature. Catalyst is filtered out, and the filtrate is evaporated tothe dry state in a vacuum.

Yield: 8.63 g (97% of theory) of a colorless, viscous oil.

Elementary analysis: C H N Cld. 57.12 10.12 7.40 Fnd. 57.10 10.00 7.39

EXAMPLE 1fN,N-Dimethyl-(3(S)-(3,5)-Acetonedimethylketal-2,2,-dimethyl-pentanoicacid)amide

8.89 g (47 mmol) ofN,N-dimethyl-(3(S)-3,5-dihydroxy-2,2,-dimethyl-pentanoic acid)amide ofthe title compound of Example 1e is dissolved in 27 ml of acetonedimethylketal, and 546 mg of camphor-10-sulfonic acid is added. It isheated for 15 hours to 50° C. It is evaporated to the dry state in avacuum, the residue is taken up in 200 ml of methylene chloride andwashed with saturated sodium bicarbonate solution, then with saturatedsodium chloride solution. The organic phase is dried on sodium sulfateand evaporated to the dry state in a vacuum. The oil that is obtained iscrystallized while standing.

Yield: 8.30 g, (77% of theory) of a colorless, crystalline solid.

Elementary analysis: C H N Cld. 62.85 10.11 6.11 Fnd. 62.90 10.00 6.00

EXAMPLE 1gN,N-Dimethyl-(5-benzyloxy-2,2,-dimethyl-3(S)-hydroxy-pentanoicacid)amide

29.8 g (0.11 mol) of N-toluenesulfonyl-D-valine (Lit.: J. Am. Chem. Soc.1937, 59, 116-118) is dissolved at 0° C. in 100 ml of dichloromethane.At 0° C., 100 ml of BH₃-THF solution (1 mol) is added in drops over 30minutes and stirred for 30 more minutes. The solution is cooled to −78°C. At −78° C., 16.42 g of benzyloxy-propanal (0.1 mol) in 100 ml ofdichloromethane and 22.4 g (0.12 mol) of1-dimethylamino-2-methyl-1-trimethylsilyl-propene of the compound ofExample 1a are stirred for 2 hours at −78° C. and for another 2 hourswhile being heated to 0° C.

5 g of NH₄F and 100 ml of MeOH are added and stirred for 18 hours atroom temperature. For hydrolysis, 150 ml of water is added. It isextracted with 200 ml of ethyl acetate, and the organic phase is washedwith 10% citric acid solution. After chromatography on silica gel withethyl acetate/hexane as an eluant, 24 g of product is obtained (85% oftheory).

The enantiomer purity was determined by means of HPLC, stat. PhaseChiracel AD 4.6×250 mm, UV 208 nm, eluant hexane/isopropanol 99:1, flow1 ml/min, t_(R) (S)=75 minutes (97%), t_(R) (R)=79 minutes (3%).

Elementary analysis: C H Cld. 68.79 9.02 Fnd. 68.65 9.08

After a reaction to form2-(2,2-dimethyl-[1,3]dioxan-4-yl)-2-methyl-butanon-3-one analogously toExamples 1e, 1f and 10, the enantiomer purity of compound 10 can beincreased after crystallization to 99% ee.

EXAMPLE 2N,N-Dimethyl-(3(S)-3,5-Di-tert-butyldimethylsilyloxy-2,2,-dimethyl-pentanoicacid)amide

7.13 g (104.75 mmol) of imidazole and 7.9 g (52.37 mmol) oftert-butyldimethylsilyl chloride are added to a solution that consistsof 3.96 g (20.95 mmol) ofN,N-dimethyl-(3(S)-3,5-dihydroxy-2,2,-dimethyl-pentanoic acid)amide ofthe title compound of Example 1e, in 20 ml of dimethylformamide, and itis stirred for 16 hours at room temperature. The solution is poured onto200 ml of water and extracted twice with 50 ml each of cyclohexane. Theorganic phases are combined and evaporated to the dry state in a vacuum.The residue is purified by flash chromatography on silica gel(hexane/MTB-ether).

Yield: 8.31 g, (95% of theory) of a colorless, viscous oil.

Elementary analysis: C H N Cld. 60.37 11.34 3.35 Fnd. 60.40 11.36 3.29

EXAMPLE 3N,N-Dimethyl-(3(S)-3,5-Cyclohexanone-dimethylketal-2,2,-dimethyl-pentanoicacid)amide

10 mg of p-toluenesulfonic acid is added to a solution that consists of3.96 g (20.95 mmol) ofN,N-dimethyl-(3(S)-3,5-dihydroxy-2,2,-dimethyl-pentanoic acid)amide ofthe title compound of Example 1e in 30.21 g (0.2095 mol) ofcyclohexanone-dimethylketal, and it is stirred for 6 hours at 100° C.The solution is poured onto 200 ml of water and extracted twice with 50ml each of ethyl acetate. The organic phases are combined and evaporatedto the dry state in a vacuum. The residue is purified by flashchromatography on silica gel (hexane/MTB-ether).

Yield: 5.08 g (90% of theory) of a colorless, viscous oil.

Elementary analysis: C H N Cld. 68.88 10.10 5.20 Fnd. 66.90 10.20 5.21

EXAMPLE 4N,N-Dimethyl-(3(S)-3,5-benzaldehyde-dimethylacetal-2,2,-dimethyl-pentanoicacid)amide

31.9 g (0.2095 mol) of benzaldehyde-dimethylacetal and 50 mg ofp-toluenesulfonic acid are added to a solution that consists of 3.96 g(20.95 mmol) of N,N-dimethyl-(3(S)-3,5-dihydroxy-2,2,-dimethyl-pentanoicacid)amide of the title compound of Example 1e, in 20 ml ofdimethylformamide, and it is stirred for 16 hours at 100° C. Thesolution is poured onto 200 ml of water and extracted twice with 50 mleach of ethyl acetate. The organic phases are combined and evaporated tothe dry state in a vacuum. The residue is purified by flashchromatography on silica gel (hexane/MTB-ether).

Yield: 5.11 g (88% of theory) of a colorless, viscous oil.

Elementary analysis: C H N Cld. 69.29 8.36 5.05 Fnd. 69.30 8.39 5.00

EXAMPLE 5aN,N-Dimethyl-(5-benzyloxy-2,2,-dimethyl-3(R,S)-acetoxy-pentanoicacid)amide

14.56 g (142.64 mmol) of acetic acid anhydride is added at 0° C. to asolution that consists of 30.65 g (109.7 mmol) ofN,N-dimethyl-(5-benzyloxy-2,2,-dimethyl-3(R,S)-hydroxy-pentanoicacid)amide of the title compound of Example 1b, 14.43 g (142.64 mmol) oftriethylamine and 200 mg of 4-dimethylaminopyridine (DMAP), dissolved in128 ml of MTB-ether, and it is stirred for 5 hours at room temperature.It is poured onto 2 l of ice water and extracted twice with 300 ml eachof MTB-ether. The combined MTB phases are washed once with 300 ml of 5%hydrochloric acid and then with water. It is evaporated to the dry statein a vacuum.

Yield: 33.50 g (95% of theory), colorless oil.

Elementary analysis: C H N Cld. 67.26 8.47 4.36 Fnd. 67.30 8.50 4.40

EXAMPLE 5bN,N-Dimethyl-(5-benzyloxy-2,2,-dimethyl-3(S)-hydroxy-pentanoicacid)amide

11.67 g (36.31 mmol) ofN,N-dimethyl-(5-benzyloxy-2,2,-dimethyl-3(R,S)-acetoxy-pentanoicacid)amide of the title compound of Example 5a is added to a buffersolution, produced from 0.88 g of potassium dihydrogen phosphate and1.82 g of disodium hydrogen phosphate in 250 ml of water. Then, 5 g ofthe enzyme lipase AYS “Amano” (related to Amano) is added, and it isstirred for 42.5 hours at room temperature. The pH is brought to 7 byadding 2.062 g of disodium hydrogen phosphate, and then it is stirredfor another 44.5 hours. Working-up: It is extracted 5 times with 400 mlof ethyl acetate. The organic phases are combined and evaporated to thedry state in a vacuum. The purification is carried out by chromatographyon silica gel (hexane/ethyl acetate gradient).

Yield: 4.60 g (40% of theory) of a colorless oil.

Elementary analysis: C H N Cld. 68.79 9.02 5.01 Fnd. 68.80 9.00 5.01

EXAMPLE 5c N,N-Dimethyl-(3(S)-3,5-dihydroxy-2,2,-dimethyl-pentanoicacid)amide

16 g of Pearlman's catalyst (Pd(OH)₂ on carbon, 20%) is added to 13.13 g(47.70 mmol) ofN,N-dimethyl-(5-benzyloxy-2,2,-dimethyl-3(S)-hydroxy-pentanoicacid)amide of the title compound of Example 5b, dissolved in 110 ml oftetrahydrofuran. It is now hydrogenated for 7.5 hours at 10 bar and atroom temperature. Catalyst is filtered out, and the filtrate isevaporated to the dry state in a vacuum.

Yield: 8.72 g (98% of theory) of a colorless, viscous oil.

Elementary analysis: C H N Cld. 57.12 10.12 7.40 Fnd. 57.10 10.10 7.39

EXAMPLE 5dN,N-Dimethyl-(3(S)-3,5-acetonedimethylketal-2,2,-dimethyl-pentanoicacid)amide

6.62 g (35.00 mmol) ofN,N-dimethyl-(3(S)-3,5-dihydroxy-2,2,-dimethyl-pentanoic acid)amide ofthe title compound of Example 5c is dissolved in 27 ml ofacetonedimethylketal, and 546 mg of camphor-10-sulfonic acid is added.It is heated for 15 hours to 50° C. It is evaporated to the dry state ina vacuum, the residue is taken up in 200 ml of methylene chloride andwashed with saturated sodium bicarbonate solution, then with saturatedsodium chloride solution. The organic phase is dried on sodium sulfateand evaporated to the dry state in a vacuum. The oil that is obtainedcrystallizes while standing.

Yield: 5.93 g, (74% of theory) of a colorless, crystalline solid.

Elementary analysis: C H N Cld. 62.85 10.11 6.11 Fnd. 62.90 10.10 6.10N-Methyl-N-phenyl-amide Synthesis

EXAMPLE 6a 1-Methyl-1-phenylamino-2-methyl-1-trimethylsilyl-propene

294 ml (0.45 ml) of butyllithium is added in drops at −35° C. underinert gas to 0.43 mol of diisopropylamine in 300 ml of THF. Then, 76.92g (0.434 mol) of N-methyl-N-phenyl-2-methylopropionic acid amide isadded in drops at 0° C. and stirred for 30 minutes at this temperature.Then, 60.3 ml (0.47 mol) of trimethylsilyl chloride is added at −35° C.and stirred for two more hours. The solvent is distilled off in a rotaryevaporator. The residue is distilled in a vacuum at 65-69° C./30 mbar.

Yield: 70.36 g (65% of theory) of an oil

Elementary analysis: C H Cld. 67.42 9.29 Fnd. 67.50 9.30

EXAMPLE 6b N-Methyl-N-phenyl-(5-benzyloxy-2,2,-dimethyl-3-oxo-pentanoicacid)amide

68.8 g (0.367 mol) of1-methyl-1-phenylamino-2-methyl-1-trimethylsilyl-propene, 81.06 g (0.401mmol) of 3-benzyloxy-propanoic acid chloride (0.4 mol) and 5.56 g>>ZnCl₂are stirred in 500 ml of THF for 1 hour. 13.88 g of NH₄F and 300 ml ofMeOH are added and stirred for 18 hours at room temperature. It isdistilled off, the residue is extracted with 200 ml of ethyl acetate,and the organic phase is washed with 10% citric acid solution. Afterchromatography on silica gel with ethyl acetate/hexane as an eluant,74.74 g of product is obtained (60% of theory).

Elementary analysis: C H Cld. 74.31 7.42 Fnd. 74.29 7.40

EXAMPLE 6cN-Methyl-N-phenyl-(5-benzyloxy-2,2,-dimethyl-3(S)-hydroxy-pentanoicacid)amide

500 mg of N-methyl-N-phenyl-(5-benzyloxy-2,2,-dimethyl-3-oxo-pentanoicacid)amide of the title compound of Example 6b is hydrogenated with acatalyst (produced from 23.3 mg of RuCl₂ (Ph)₂ and 62.6 mg of S-BiNAPaccording to R. Selke, Angew. Chem. 1998, 110, 1927-1930) (2 days at 40°C./100 bar).

Yield: quantitative

Elementary analysis: C H Cld. 73.87 7.97 Fnd. 74.00 8.00

EXAMPLE 6d N-Methyl-N-phenyl-(3(S)-3,5-dihydroxy-2,2,-dimethyl-pentanoicacid)amide

16 g of Pearlman's catalyst (Pd(OH)₂ on carbon, 20%) is added [to] 16.29g (47.70 mmol) ofN-methyl-N-phenyl-(5-benzyloxy-2,2,-dimethyl-3(S)-hydroxy-pentanoicacid)amide of the title compound of Example 6c, dissolved in 110 ml oftetrahydrofuran. It is now hydrogenated for 7.5 hours at 10 bar and atroom temperature. Catalyst is filtered out, and the filtrate isevaporated to the dry state in a vacuum.

Yield: 11.98 g (98% of theory) of a colorless, viscous oil.

Elementary analysis: C H N Cld. 66.91 8.42 5.57 Fnd. 66.90 8.40 5.60

EXAMPLE 6eN-Methyl-N-phenyl-(3(S)-(3,5)-acetonedimethylketal-2,2,-dimethyl-pentanoicacid)amide

11.81 g (47 mmol) ofN-methyl-N-phenyl-(3(S)-3,5-dihydroxy-2,2,-dimethyl-pentanoic acid)amideof the title compound of Example 6d is dissolved in 27 ml ofacetonedimethylketal, and 546 mg of camphor-10-sulfonic acid is added.It is heated for 15 hours to 50° C. It is evaporated to the dry state ina vacuum, the residue is taken up in 200 ml of methylene chloride andwashed with saturated sodium bicarbonate solution, then with saturatedsodium chloride solution. The organic phase is dried on sodium sulfateand evaporated to the dry state in a vacuum. The oil that is obtainedcrystallizes while standing.

Yield: 10.54 g, (77% of theory) of a colorless, crystalline solid.

Elementary analysis: C H N Cld. 70.07 8.65 4.81 Fnd. 70.00 8.50 4.90

EXAMPLE 7N-Methyl-N-phenyl-(3(S)-3,5-cyclopentanonedimethylketal-2,2,-dimethyl-pentanoicacid)amide

10 mg of p-toluenesulfonic acid is added to a solution that consists of5.26 g (20.95 mmol) ofN-methyl-N-phenyl-(3(S)-3,5-dihydroxy-2,2,-dimethyl-pentanoic acid)amideof the title compound of Example 6d) in 30.21 g (0.2095 mol) ofcyclopentanone-dimethylketal, and it is stirred for 6 hours at 100° C.The solution is poured onto 200 ml of water and extracted twice with 50ml each of ethyl acetate. The organic phases are combined and evaporatedto the dry state in a vacuum. The residue is purified by flashchromatography on silica gel (hexane/MTB-ether).

Yield: 5.98 g (90% of theory) of a colorless, viscous oil.

Elementary analysis: C H N Cld. 71.89 8.57 4.41 Fnd. 71.90 8.60 4.50

EXAMPLE 8N-Methyl-N-phenyl-(3(S)-3,5-dichlorodiphenylsilane-2,2,-dimethyl-pentanoicacid)amide

3.14 g (46.09 mmol) of imidazole and 5.83 g (23.05 mmol) ofdichlorodiphenylsilane are added to a solution that consists of 5.26 g(20.95 mmol) ofN-methyl-N-phenyl-(3(S)-3,5-dihydroxy-2,2,-dimethyl-pentanoic acid)amideof the title compound of Example 6d, in 20 ml of dimethylformamide, andit is stirred for 16 hours at room temperature. The solution is pouredonto 200 ml of water and extracted twice with 50 ml each of methylenechloride. The organic phases are combined and evaporated to the drystate in a vacuum. The residue is purified by flash chromatography onsilica gel (hexane/MTB-ether).

Yield: 7.68 g (85% of theory) of a colorless, viscous oil.

Elementary analysis: C H N Cld. 72.35 6.77 3.25 Fnd. 72.37 6.80 3.30

EXAMPLE 9a rac. N,N-Dimethyl-(3-hydroxy-3-oxo-pentanoic acid)amide

13 ml (26 mmol) of a 2 mol LDA-THF solution is added at −50° C. to 2.99g (26 mmol) of N,N-dimethyl-2-methylpropinonic acid amide and stirredfor 30 minutes at this temperature. Then, 1.44 g (20 mmol) ofpropiolactone is added, and it is stirred for 20 more hours while beingheated to room temperature. It is hydrolyzed with saturated ammoniumchloride solution and extracted with ethyl acetate. After drying at 1mbar, 2.8 g of Example 9a (77% of theory) is obtained.

Elementary analysis: C H N Cld. 57.72 9.15 7.47 Fnd. 58.05 8.95 7.75

EXAMPLE 9b N,N-Dimethyl-3(S)-(3,5-dihydroxy-2,2,-dimethyl-pentanoicacid)amide

1.87 g (10 mmol) of rac. N,N-dimethyl-(3-hydroxy-3-oxo-pentanoicacid)amide of the title compound of Example 1c is hydrogenated with acatalyst (produced from 75 mg of RuCl₂ (Ph)₂ and 190 mg of S-BiNAPaccording to R. Selke, Angew. Chem. 1998, 110, 1927-1930) (2 days at 40°C./100 bar).

Yield: quantitative

Elementary analysis: C H N Cld. 57.11 10.1 7.4 Fnd. 57.60 10.3 7.7

EXAMPLE 10 (S)-3-(2,2-Dimethyl-[1,3]dioxan-4-yl)-3-methyl-butan-2-one

35.6 ml of methyllithium-lithium bromide complex (1.5 M in diethylether) is added in drops at −20° C. to 4.08 g (17.79 mmol) of the titlecompound of Example 1f,N,N-dimethyl-(3(S)-3,5-acetonedimethylketal-2,2,-dimethyl-pentanoicacid)amide, dissolved in 5 ml of diethyl ether. Then, it is stirred for30 minutes at −20° C. and then heated to room temperature. It is stirredovernight at room temperature. 10 ml of saturated ammonium chloridesolution is added, and it is stirred for 6 hours at room temperature.The organic phase is separated and washed twice with water. The organicphase is evaporated to the dry state in a vacuum. The purification iscarried out by chromatography on silica gel (hexane/ethyl acetategradient).

Yield: 2.77 g (78% of theory) of an oil.

Elementary analysis: C H Cld. 65.97 10.07 Fnd. 65.84 10.19

EXAMPLE 11 (S)-2-(2,2-Dimethyl-[1,3]dioxan-4-yl)-2-methyl-heptan-3-one

34 ml of n-butyllithium 15% (1.6 M in hexane) is added in drops at −65°C. to 4.08 g (17.79 mmol) of the title compound of Example 1f,N,N-dimethyl-(3(S)-3,5-acetonedimethylketal-2,2,-dimethyl-pentanoicacid)amide, dissolved in 5 ml of THF. Then, it is stirred for 5 hours at−65° C. and then heated to room temperature. It is stirred overnight atroom temperature. 10 ml of saturated ammonium chloride solution isadded, and it is stirred for 6 hours at room temperature. The organicphase is separated and washed twice with water. The organic phase isevaporated to the dry state in a vacuum. The purification is carried outby chromatography on silica gel (hexane/ethyl acetate gradient).

Yield: 4.13 g (96% of theory) of an oil.

Elementary analysis: C H Cld. 69.38 10.81 Fnd. 69.27 10.96

EXAMPLE 12 (4S)-4-(2-Methyl-3-oxo-hept-6-en-2-yl)-2,2-dimethyl-[1,3]dioxane

50 ml of 3-butenyllithium solution (produced from 4-bromo-1-butene andlithium wire or tert-butyllithium, according to J. Org. Chem. Vol. 56,No. 21, pp. 6094-6103 (1991) or J. Chem. Soc. Perkin Trans. 1 pp. 2937,(1988)) is added in drops at −90° C. to 4.08 g (17.79 mmol) of the titlecompound of Example 1 f,N,N-dimethyl-(3(S)-3,5-acetonedimethylketal-2,2,-dimethyl-pentanoicacid)amide, dissolved in 5 ml of diethyl ether. Then, it is stirred for17 hours at −90° C. and then heated to room temperature. It is stirredovernight at room temperature for 17 hours. 10 ml of saturated ammoniumchloride solution is added, and it is stirred for 6 hours at roomtemperature. The organic phase is separated and washed twice with water.The organic phase is evaporated to the dry state in a vacuum. Thepurification is carried out by chromatography on silica gel(hexane/ethyl acetate gradient).

Yield: 2.74 g (70% of theory) of a colorless oil

Elementary analysis: C H Cld. 69.96 10.06 Fnd. 69.90 10.05

EXAMPLE 13 N,N-Dimethyl-2,2-dimethyl-pentane-1,5-dicarboxylicacid-1-amide-5-ethyl ester

0.81 g (5.35 mmol) of malonic acid monoethyl ester chloride is added at0° C. to 1 g of 1-dimethylamino-2-methyl-1-trimethylsilyl-propene (5.35mmol); 72 mg of anhydrous ZnCl2 is subsequently added as catalyst, andit is stirred for 2 hours at 0° C. It is added to 10 ml of water,chromatographed twice with 10 ml each of ethyl acetate andchromatographed on silica gel.

Yield: 0.958 g (77% of theory).

MS-CI/NH₃ (70 eV), M/Z=230 [M−H]⁺

¹H-NMR (300 MHz, CDCl₃, 25° C., TMS) δ=01.4 (s, 6H), 2.9 (m, 6H), 3.48(s, 2H), 4.25 (m, 4H)

Abbreviations of the Ether Protective Groups that are Used:

-   TES=Triethylsilyl-   TMS=Trimethylsilyl-   TIP=Triisopropyl-   TBDPS tert-Butyl-dimethylsilyl-   MEM=Methylethoxymethyl-   MOM=Methyloxymethyl-   THP=Tetrahydropyranyl-(ether)    Abbreviations of the Ether Protective Groups that are Used:-   TES=Triethylsilyl-   TMS=Trimethylsilyl-   TIP=Triisopropyl-   TBDPS=tert-Butyl-dimethylsilyl-   MEM=Methylethoxymethyl-   MOM=Methyloxymethyl-   THP=Tetrahydropyranyl-(ether)

The entire disclosures of all applications, patents and publications,cited herein and of corresponding German application No. 101 38 348.7,filed Aug. 3, 2001, and U.S. Provisional Application Ser. No.60/313,015, filed Aug. 20, 2001, are incorporated by reference herein.

The preceding examples can be repeated with similar success bysubstituting the generically or specifically described reactants and/oroperating conditions of this invention for those used in the precedingexamples.

From the foregoing description, one skilled in the art can easilyascertain the essential characteristics of this invention and, withoutdeparting from the spirit and scope thereof, can make various changesand modifications of the invention to adapt it to various usages andconditions.

1. A compound of the formula I:

in which R₁ and R₂ are the same or different and, independently of oneanother, stand for an alcohol protective group or, R₁ and R₂ are bridgedand together stand for a ketal protective group, and Y stands for agroup -NA1A2, whereby A1 and A2, independently of one another, stand forC₁-C₆ alkyl, aryl, aralkyl, —OH, —OMe, or —O-benzyl, or Y stands for

where the dashed line bonds indicate the point of attachment.
 2. Acompound of claim 1, wherein the alcohol protective groups are selectedfrom: benzyl, 4-methoxybenzyl, 3,4-dimethoxybenzyl, THP, TBDMS, TMS,TES, TIP, TBDPS, MEM, MOM, allyl and trityl groups; and the ketalprotective group is selected from groups of the following formulae:

where the dashed line bonds indicate the points of attachment.
 3. Acompound of claim 1, wherein for A1 and A2, aryl is phenyl and aralkylis benzyl.
 4. A compound of claim 1, which is of the formula Ia:

in which R₁, R₂ and Y have the meanings given in claim
 1. 5. A compoundof claim 1, which is of the formula Ib:

in which R₁, R₂ and Y have the meanings given in claim
 1. 6. A compoundof claim 4, which isN,N-dimethyl-(3(S)-(3,5)-acetonedimethylketal-2,2,-dimethyl-pentanoicacid)amide of the formula:


7. A compound of claim 4, which isN,N-dimethyl-(3(S)-3,5-benzaldehyde-dimethylacetal-2,2-dimethyl-pentanoicacid)amide of the formula:


8. A compound of claim 4, which isN,N-dimethyl-(3(S)-3,5-di-tert-butyldimethylsilyloxy-2,2,-dimethyl-pentanoicacid)amide of the formula:


9. A compound of claim 4, which isN,N-dimethyl-(3(S)-3,5-cyclohexanone-dimethylketal-2,2,-dimethyl-pentanoicacid)amide of the formula:


10. A compound of claim 4, which isN-methyl-N-phenyl-(3(S)-(3,5)-acetonedimethylketal-2,2,-dimethyl-pentanoicacid)amide of the formula:


11. A compound of claim 4, which isN-methyl-N-phenyl-(3(S)-3,5-cyclopentanonedimethylketal-2,2,-dimethyl-pentanoicacid)amide of the formula:


12. A compound of claim 4, which isN-methyl-N-phenyl-(3(S)-3,5-diphenylsilanoxy-2,2,-dimethyl-pentanoicacid)amide of the formula:


13. A compound of formula II:

in which Y stands for a group -NA 1A2, where A1 and A2, independently ofone another, stand for C₁-C₆ alkyl, aryl, aralkyl, —OH, —OMe, or—O-benzyl, or Y is

where the dashed line bonds indicate the point of attachment.
 14. Acompound of claim 13, wherein the configuration at the C-atom of thesecondary alcohol is S.
 15. A compound of claim 13, wherein theconfiguration at the C-atom of the secondary alcohol is R.
 16. Acompound of claim 13, wherein for A1 and A2, aryl is phenyl and aralkylis benzyl.
 17. A compound of claim 13, which isN,N-dimethyl-(3(S)-(3,5-dihydroxy-2,2,-dimethyl-pentanoic acid)amide ofthe formula:


18. A compound of formula III:

in which R₁ stands for an alcohol protective group, and Y stands for agroup -NA 1A2, where A1 and A2, independently of one another, stand forC₁-C₆ alkyl, aryl, aralkyl, —OH —OMe or —O-benzyl, or Y is

where the dashed line bonds indicate the point of attachment.
 19. Acompound of claim 18, wherein the alcohol protective group is selectedfrom: benzyl, 4-methoxybenzyl, 3,4-dimethoxybenzyl, THP, TBDMS, TMS,TES, TIP, TBDPS, MEM, MOM, allyl and trityl groups.
 20. A compound ofclaim 18, wherein for A1 and A2, aryl is phenyl and aralkyl is benzyl.21. A compound of claim 18, wherein the configuration at the C-atom ofthe secondary alcohol is S.
 22. A compound of claim 18, wherein theconfiguration at the C-atom of the secondary alcohol is R.